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Front ABS Sensor Replacement
 
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Pelican Technical Article:

Front ABS Sensor Replacement

Jared Fenton

Time:

1 hour1 hr

Tab:

$80

Talent:

***

Tools:

Pliers, penetrant spray

Applicable Models:

A6 2.7T (1997-04)
A6 2.8 (1997-02)
A6 3.0L (2002-04)
S6 4.2 (1997-04)

Parts Required:

Front ABS Sensor

Hot Tip:

Use penetrant spray before removing the sensor.

Performance Gain:

Working ABS system

Complementary Modification:

Replace brake pads

The ABS wheel speed sensor monitors the rotation rate of the road wheel and sends an electronic signal to the ABS module. This signal is used to calculate road wheel speed to help with braking and stability control features. When an ABS wheel speed sensor fails, the ABS module loses road wheel speed signal for that wheel and sets a fault code for ABS wheel speed signal. When a fault code is set, the ABS warning light illuminates. You have to use a diagnostic scanner or code reader to read the fault codes to determine which speed sensor is the problem. Keep in mind that other problems can illuminate the ABS warning light, so be sure to scan and read fault codes before you start replacing expensive parts.

Sometimes, you get lucky and the sensor only needs to be cleaned as brake dust and dirt can sometimes affect the operation of the sensor. If you get a fault code and it points out a failure with a sensor, you may want to remove and clean it before buying a new one. If the fault code reappears, you may have to replace it.

Begin by jacking up and supporting the front of the car on jackstands. For more information please see our article on Jacking up your Audi A6. Remove the front wheels and look directly behind the brake rotor at the front. You will see a wire harness leading into the front of the wheel hub. On early A6 models, the sensor is a press fit. On later cars, you'll see a T25 Torx bolt holding the sensor into the hub. Remove the screw.

Usually, removing the sensor from the hub is a simple matter of pulling it up and out of the hub. More often, the sensor will be stuck and will require some force to remove it. If the sensor is stuck, spray a good penetrant spray around the base and let it soak in for a few hours. Use a pair of pliers and gently walk the sensor back and forth to break it free.

Once the sensor is removed, clean the inside of the housing with brake cleaner. If there is any corrosion inside the bore, clean it off using a wire brush. You'll want to install the new sensors with a thin coating of anti-seize compound to the ABS sensor and the inside of the housing.

Shown here is a new front ABS sensor for the C5 Audi A6, available from Pelicanparts.
Figure 1

Shown here is a new front ABS sensor for the C5 Audi A6, available from Pelicanparts.com

The ABS sensor is located at the front of each front wheel bearing hub as shown here (green arrow).
Figure 2

The ABS sensor is located at the front of each front wheel bearing hub as shown here (green arrow). Early A6 models have a press fit sensor that needs to be pulled out. Later models have a T25 Torx screw that must be removed first.

Clean the inside of the sensor housing (green arrow) with a wire brush and cleaner before installing the new sensor.
Figure 3

Clean the inside of the sensor housing (green arrow) with a wire brush and cleaner before installing the new sensor.

Press the tab on the brake pad wear indicator electrical connector (green arrow) and pull it off.
Figure 4

Press the tab on the brake pad wear indicator electrical connector (green arrow) and pull it off.

Once the brake pad wear indicator is disconnected, pull the ABS sensor wiring harness out of the metal locating tab (green arrow).
Figure 5

Once the brake pad wear indicator is disconnected, pull the ABS sensor wiring harness out of the metal locating tab (green arrow).

Now pull the ABS sensor wiring harness out of the locating clips (green arrows) on the inner fender well.
Figure 6

Now pull the ABS sensor wiring harness out of the locating clips (green arrows) on the inner fender well.

Use a screwdriver to pry out the grommet (green arrow) at the top of the wiring harness.
Figure 7

Use a screwdriver to pry out the grommet (green arrow) at the top of the wiring harness. You'll need to access the electrical connectors inside.

Pull the electrical connectors for the harness out and pry open the two tabs on each connector (green arrows).
Figure 8

Pull the electrical connectors for the harness out and pry open the two tabs on each connector (green arrows). Now pull the connectors apart.

Pull the wiring harness down through the hole in the upper control arm (green arrow).
Figure 9

Pull the wiring harness down through the hole in the upper control arm (green arrow).

Pull the remainder of the wiring harness through the hole in the upper control arm (green arrow).
Figure 10

Pull the remainder of the wiring harness through the hole in the upper control arm (green arrow). New ABS sensor installation is reverse of removal.


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Page last updated: Tue 10/17/2017 03:29:28 AM